Each
spring there is a certain turning point when I know that it is time
to get out my nets and collecting bottles and head for the nearest
pond. After many years, I have learned to sense when that burst of
life and energy will appear and a rich variety of forms will be
actively producing a harvest for my nets. For me, the ideal times to
collect are the spring and autumn or what I call the pre- and
post-mosquito seasons. In early and midsummer, they occur in
oppressive swarms around open water and, of course, now there is the
addition of the potentially serious discomfort of West Nile fever
but, in the spring, the explosion of aquatic protists and
invertebrates makes every trip into the field an exciting adventure.
These waters are filled with marvels and mysteries that one could
only begin to address in a hundred lifetimes.

Every
year, I set out with a sense of anticipation and joy, for every year
I have found organisms that I had never previously seen and I have
had the fun of trying to study them and identify them and, if I get
lucky, produce some good photographs of them. Part of the joy is the
challenge for each time, I am aware that I am entering a world so
marvelously alien that it convinces me that all of the really good
science fiction writers are or were closet microscopists. What
astonishes me over and over is that here is a multitude of hidden
universes all around us which 99% of the world’s population is
totally or nearly completely unaware of. I like to think of the
amateur microscopists and natural historians as explorers who have
before them the exhilaration of inexhaustible adventures. The fact
that others have seen, described and studied the splendid desmid
Micrasterias
in no way detracts from my elation in observing and investigating it.

There
are many examples of such elaborate kinds of geometric forms in
nature and so it is not surprising that historically God was often
thought of as a mathematician. Consider the marvelous radial
symmetry of radiolaria. Of course you won’t find these in
ponds, since they are exclusively marine.

This
sort of lovely mathematical precision can be found in heliozoan
amoebae such as Actinosphaerium.

Also
a similar sort of pattern occurs in many echinoids, such as,
Heterocentrotus
mammilatus.
You can even find a striking visual parallel in a horse chestnut,
but its radial symmetry is based on a four-fold symmetry whereas that
of regular echinoids is based on a pentagonal or five-fold symmetry.
When we find these kinds of striking visual examples, we are often
tempted to make generalizations about patternings that are
morphologically unsound, even though they may be aesthetically and
psychologically pleasing. Mandelbrot’s work, The
Fractal Geometry of Nature,
reveals something enormously important for us whenever we want to
think about patterning in nature. For our purposes, perhaps the
central and most illuminating concept is that the reiteration of a
particular structural pattern always involves differences between the
particular instance we are examining and every other instance. In
other words, there is no Platonic eidos
that is the absolute ideal form for the particular real cases. I
know this isn’t very clear and yet the basic notion is
startlingly simple. Let me try to explain. In attempting to deal
with the extraordinary complexity of the world, we develop categories
and subcategories and enormous systems of classification for
everything from inanimate objects to flora and fauna and humans and
even our behaviors and institutions. This is especially true when we
engage ourselves with science. It is obvious that we cannot have a
science of the particular; we must rely on groupings and
classifications. We think of human beings as individuals or
singularities–sometimes! They are assigned specific names
which with regard to our friends, enemies, relatives, acquaintance,
and public figures, we know but, of course, most of the people on the
planet are anonymous for us. There are 1.7 billion Chinese and I
don’t know any one of them by his or her individual name. We
give names to our pets and certain animals in a zoo, but imagine what
a total mental meltdown we would face if we started trying to give
individual names to our Paramecia in a large, rich culture and here
is where I finally get to the point. Identical twins aren’t
identical and this becomes evident as they are enculturated. No two
Paramecia are identical, but the differences are generally so slight
that we can’t detect them; they are like even more subtle
versions of the Mandelbrot “turtle” in that each
individual is a singularity. Well, enough of this digression; it’s
just that I find the notion fascinating. Of course, being unique is
not necessarily a virtue as is daily evidenced in the human
population. A final word on this issue: remember that when you are
observing a particular organism and you think to yourself–oh
yes, I’ve seen this creature before, so I don’t need to
spend much time examining it–you
might be quite wrong. The one you previously observed might have
been a mutant, a “monster” formation, an immature form, a
specimen which was parasitized, and the possibilities go on.

So,
back to spring harvest. Another desmid which frequently appears in
samples is the lovely crescent-shaped Closterium.

This
organism has wonderfully intricate chloroplasts and at each tip, a
spherule containing minute granules which are in constant motion.

The
aforementioned Paramecia are, of course, in evidence and one can
quickly and readily produce rich cultures of them by adding a boiled
wheat grain to some boiled pond water or some artesian water from
your grocery store; they sell it by the gallon for about a dollar.
Let the dish sit for 2 or 3 days to develop a good bacterial growth
and then inoculate the dish with a few Paramecia. They are amazing
organisms which are often treated quite casually because they are so
common. In another sense, however, they are quite uncommon, that is,
unusual.

These
are images of living Paramecia taken using Nomarski Differential
Interference Contrast. This is a wonderful technique for certain
kinds of specimens. Its major disadvantage is that this system
regards even a Paramecium as being quite thick and so a Nomarski
system produces a series of optical sections of “slices”
which means that you can use it as a kind of optical microtome
without having to kill and embed your specimen. The great advantage,
of course, is that you have something rather like Computer Assisted
Tomography–a CAT scan–especially if you have some
computer stacking software, such as, Helicon Focus which will allow
you to take a series of images just altering the focal plane by a few
microns each time and then using the software to produce a single
combined image. The results can be very impressive.

However,
at this point let’s go back to the first Nomarski image of the
Paramecium. The detail which is revealed–and this is a single
image, not a composite one–is quite remarkable. You can see
the macronucleus, the contractile vacuoles, the cilia, the capsules
along the edge of the membrane which house the trichocysts, and all
sorts of internal granules.

The
reason I have been going on at such length about Paramecium is that
textbooks often present it as a “typical” ciliate
whereas, in fact, it is anything but. Even within the genus, there
is a lot of variation. Paramecium
caudatum,
P.
aurelia,
and P.
multimicronucleatum
are perhaps the most common species. P.caudatum
has
been studied extensively and is often taken as the prototypical
species. P.
aurelia has
also been the focus of intensive research both in terms of aging and
mating types. Paramecia present us with a complex behavior which we
might very well not anticipate–SEX!

P.
aurelia,
depending upon the suspecies or variant, divides about 200 to 250
times before it needs recharging of its genetic material by means of
conjugation and the exchange of micronuclei with a different mating
type. The problem is that we haven’t yet learned how to
distinguish mating types, but the Paramecia manage it. When it all
goes smoothly, then they can start dividing again and as long as they
keep repeating the process, they achieve a kind of theoretical
“immortality”.

There
is another strain of Paramecium which harbors a genetic fragment know
as a “kappa” particle. When it conjugates with a
non-kappa strain, some of the kappa particles get transmitted when
the micronuclei are exchanged and these particles turn out to be
lethal to the non-kappa strain thus allowing the kappa strain to
maintain a kind of dominance.

P.
multimicronucleatum,
as its name suggests, has a large number of micronuclei, whereas
other species may have only 2 or 4. The biological advantages of
this are not altogether clear. Another species, P.
bursaria,
possesses symbiotic algae (Chlorella)
and their photosynthetic activity helps provide food for the larger
organism. However, when the light conditions are poor so that the
symbionts can no longer do this, the Paramecium digests them.

Another
puzzle about Paramecia is the trichocysts. These are easily
demonstrated by adding a drop of dilute tannic acid to the edge of a
cover glass on a slide containing Paramecia. The trichocysts are
ejected with considerable force and sometimes to an astonishing
distance, relatively speaking, yet they don’t seem to do
anything

They
don’t’ appear to have any offensive or defensive
significance and yet they are abundant and require a considerable
amount of energy both in their production and in their discharge.

In
order to not completely neglect the title of this essay, I am going
to devote the rest of it to a small gallery of images with very brief
comments and I shall make every effort to avoid going off on tangents
(a difficult task for me).

A
Mini-Gallery of Some Likely Spring Pond Organisms

This
is a Cladoceran which is a micro-crustacean, related to another
wonderful spring creature, the “water flea”, Daphnia.

This
is Amoeba
proteus,
one of the largest amoebae, which is surprisingly difficult to find
in nature but, fortunately cultures easily.

Stentor
coeruleus is
the marvelous “trumpet-shaped” ciliate with the
distinctive and unique dichroic pigment called “stentorin”.
In most situations, it presents itself as a blue-green but, in
certain angles of illumination, it takes on a rosy-pink hue.

Bursaria
truncatella is
one of my favorites and whenever I see it, I think of an elegant,
animated Steuben crystal vase sliding through the water.
Unfortunately, I have not had the best of luck in capturing good
images of it, so you’ll have to settle for the one above.

Another
group of frequent spring and summer pond denizens is water mites.
The one I encounter most frequently is a brilliant scarlet color, but
there are others which are brown, orange, light-greenish gray, and
some that are brown with yellow spots.

Spirogyra
is
perhaps the commonest and one of the most delightful of the
filamentous algae. Its name is most fitting, for you can see the
chloroplasts forming a green spiral in each of the segments. It has
a complex life cycle and you should always keep an eye out for
conjugating strands.

Spirostomum,
a giant among ciliates, is also readily found, especially in ponds
where cows or wild ruminants come to drink and often leave behind
feces. Spirostomum
thrives
in such environments rich in organic material. S.
ambiguum
often exceeds 2000 microns in length and is highly contractile. Like
Paramecia, the species of Spirostomum
vary
considerably and some are much smaller and have only a single ovoid
macronucleus whereas others have long chain or beaded macronuclei.

Here
is a specimen of S.
minus which
I stained with Methyl Green Acetic and you can clearly see the long
macronucleus in spite of the distortion of the organism.

In
this specimen of Euglena,
you can see the red eye spot, the chloroplasts, and one of the
flagella. Euglenoids frequently have a trailing flagellum (or two or
three) which are often difficult to observe. This is where phase
contrast becomes exceptionally valuable.

If
you are patient and search carefully, you may have the good fortune
to come across a suctorian. These are one of the oddest of the
ciliates and pose a real challenge for taxonomists. They do have a
free-swimming stage which is ciliated, but once they “settle
down”, they produce tentacles. You can see that an unfortunate
ciliate, larger than the suctorian, has gotten trapped by one of the
adhesive pads at the tip of a tentacle and the suctorian is indeed
sucking its protoplasm through its tentacle like a straw.

The
spring is also a splendid time to collect diatoms which occur in a
mind-boggling variety of shapes and sizes. There are two major
groupings, the centric and the pennate diatoms. Below, I will show
you an example of each.

The
majority of diatoms occur as single individuals, but quite a few
occur as aggregates or shins of individuals and some of these are
strikingly beautiful. For nearly 2 centuries, microscopists have
been so taken with diatoms that they have made arrangements of them.
Below is a modest example of an exhibition slide.

In
the 19th
Century, J.D. Moeller and his brother produced a diatom exhibition
slide containing over 4000 diatoms!

Rotifers
also occur in a staggering variety of forms, sizes and shapes. The
specimen above is of the genus Keratella
and
I stained it with a drop of Basic Fuchsin. You can see the sculpting
on its protective envelope. This is the rotifer that I think looks
rather like a Klingon warship. There are also colonial forms, such
as, Conochilus
and
tube-dwelling forms, some of which, such as Floscularia,
construct the tube out of its own fecal pellets.

Another
pigmented ciliate which often shows up in samples is Blepharisma,
most species of which are pink, although there are some blue ones and
some that are albino. They are fairly closely related to Spirostomum,
but they do not exhibit the contractility so characteristic of
Spirostomum.

These
protists could never be presented as examples of a typical ciliate.
In addition to possessing a distinctive pigment, they readily form
distinctive and unusual cysts, they are voracious feeders and under
certain conditions start eating each other and form what are known as
“cannibal giants”.

Finally,
a creature that I find in abundance in my spring collections is the
ostracod also know as “seed shrimp”. I think of them as
micro-versions of Pac-Man.

This
particular species has a distinctively rich green color They show
considerable color variation and the pigment seems to be embedded in
the valves of the shell. Some are brown, others light yellow to
light orange, some are almost black and others possess very little
observable pigmentation. These micro-crustaceans seem to be
incessantly scurrying around feeding or seeking food–if you
watch them for more than 10 minutes, you’ll feel exhausted.

For
me, spring collecting is a special delight after a long winter of
snow, wind, and frozen ponds and lakes. Don’t get me wrong, I
love the special character of our winters– I could never live
in Bagdad or Tucson–but the seasonal explosion of life forms
after a winter of hibernation is a glorious thing to experience.